Planting CRYSTALS-Kyber Acceleration Seeds

CRYSTALS-Kyber (FIPS203) was one of the first post quantum cryptography schemes to be standardized by the National Institute of Standards and Technology; CRYSTALS-Kyber utilizes Montgomery reduction at the heart of the modulo reduction. Montgomery reduction traditionally is suited to computing moduli much larger than 32/64-bits. Recently a new modulo reduction method was published named Plantard reduction which allows for one less multiplication at the reduction stage. However, this does require doubling the word size of the values being calculated, in the case of CRYSTALS-Kyber increasing from 16-bit to 32-bit. In this paper we present the worlds first Plantard ISE on the Ibex RISC-V core and investigate the impact Instruction Set Extensions can have utilizing this new modulo reduction method over original methods such as Montgomery and Barrett reduction. Utilizing Plantard reduction as a set of Instruction Set Extensions, we are able to reduce the cycle counts required to compute the entire CRYSTALS-Kyber algorithm by up to 21% and reduce the cycle counts of the NTT by 1.7x and the INTT by 2.6x against the reference implementation.